New mobile phone automatic power off charger circuit principle

Mobile phone crystal 3.2*2.5mm 3225 26M (26.000MHZ) 7.5PF 10PPM 20PPM 30PPM

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Overview:
With the continuous development of society, the continuous improvement of living standards and the increasing work intensity, mobile phones as a portable mobile communication device have become more and more essential for people's daily life. With the widespread promotion of mobile phones, the consumables of related consumables will also rise. The charger (power adapter) is a must-have for the battery power of mobile phones, and its usage is no less than that of mobile phones. How to reduce the power consumption of the charger and the power consumption in the full state will become a problem that the whole society must face.
Most mobile phone users save time after charging their mobile phones, and they don’t pull out the plugs for the next charge. This wastes power and creates huge security risks. According to recent survey data from Nokia, the mobile phone consumes more than 60% of its total energy usage in no-load mode (the charger is plugged into a wall outlet but not connected to the mobile phone). More than 3/4 of the power consumption is caused by the user not charging the charger after the mobile phone is fully charged. At present, there are more than 600 million mobile phone users in China, which is a great waste. According to preliminary statistics, the mobile phone will not be plugged after charging, and the annual power consumption will exceed 2 billion kWh, which is equivalent to 4% of the power generated by Gezhouba Hydropower Station.
To this end, the author designed a charger that can automatically power off the mobile phone charger to achieve the purpose of zero power consumption of the original coil when the mobile phone charger is empty and the battery is full, to save resources and start from the side.

1 program design and hardware components
1.1 Scheme design Compared with the existing power-off charger, the advantage of this product is that it can not only automatically power off when fully charged, but also automatically power off when the mobile phone is manually unplugged, to achieve automatic power-off. Figure 1 shows the internal circuit diagram.
Working principle: After connecting the charger to the mobile phone and the socket, the voltage is adjusted by the resistor, and enters the voltage comparator with a small value to output a rated value, which is the normal charging of the mobile phone. When the mobile phone is fully charged, there is a voltage comparator that is larger than the other end voltage, and the output is 0V. At this time, the relay sucks the armature to disconnect the circuit and realize automatic power-off.

Figure 1 internal circuit diagram

1.2 Hardware components
1.2.1 Relays use micro-relays to achieve on-off control of the circuit. When not fully charged, the upper armature pulls in and the mobile phone is normally charged; when the charger is fully charged, the upper armature is disconnected, causing the circuit to be disconnected instantaneously to achieve automatic power off.
1.2.2 Voltage Comparator Use the comparator voltage comparator to achieve the desired voltage output. The voltage comparator can be thought of as an op amp with a magnification close to "infinity." Function of the voltage comparator: Compare the magnitude of the two voltages (using the high or low level of the output voltage to indicate the magnitude relationship between the two input voltages):
When the "+" input voltage is higher than the "-" input, the voltage comparator output is high;
When the “+” input voltage is lower than the “-” input, the voltage comparator output is low.
One end of the voltage comparator is connected to the input voltage point and the other end is grounded. Pre-set a reference voltage of 0.2V. When the input voltage is less than 0.2V, pass the voltage of the voltage comparator at the end of the voltage u1 < 0.2V, and output a suitable voltage to make the circuit work normally. When the charging is completed, pass the voltage of the comparator. > 0.2V, the comparator output voltage is 0V, the relay armature is disconnected, the circuit is instantly disconnected, and the automatic power off is realized.
1.2.3 Diode circuits are used multiple times to prevent current reflow, and their respective functions are different.
(1) Adopt 1N4007 type diode.
Function: 1. When the mobile phone is fully charged, the performance of diode diode conduction is used to prevent current from flowing backwards. (2) When the positive and negative terminals of the mobile phone battery are reversed, the battery can be protected and the service life can be extended.
Adopting IN4148, it is a small high-speed switching diode with relatively fast switching. It is widely used in single-pass isolation for circuits with high signal frequency, and is commonly used in communication, computer boards, TV circuits and industrial control circuits.
1.2.4 Capacitor Use 22u/10V capacitor to control the stability of the relay action. Capacitance can store the charge under a given potential difference. When the mobile phone is not full, the capacitor stores the charge. When the battery is about to be full, the capacitor discharges the charge, the circuit current is stable, and the relay does not swing the armature up and down due to the unstable current. , to facilitate automatic power off.
1.2.5 Resistance (R9/10K)
Here, a 10 kΩ resistor is used in parallel with the comparator to prevent the relay from swinging up and down due to current instability, which is beneficial to automatic power-off.
1.2.6 Reset Switch In order to reduce the user's trouble, select the reset switch (SW-PB) to achieve automatic reply. The principle is as follows: when the switch is pressed for a moment, the circuit is turned on instantaneously. When the switch is released, the switch is disconnected from the circuit, and the circuit is instantaneously turned on to make it work normally.
(Please read the PDF for details)